1. Field of the Invention
The invention disclosed and claimed herein generally pertains to a method and related apparatus for data transfer between multiple root nodes and PCI adapters, through an input/output (I/O) switched-fabric bus. More particularly, the invention pertains to a method of the above type wherein different root nodes may be routed through the I/O fabric to share the same adapter, so that it becomes necessary to provide a single control to configure the routing for all root nodes. Even more particularly, the invention pertains to a method of the above type wherein the routing configuration control resides in a specified one of the root nodes.
2. Description of the Related Art
As is well known by those of skill in the art, the PCI family (Conventional PCI, PCI-X, and PCIe) is widely used in computer systems to interconnect host units to adapters or other components, by means of an I/O switched-fabric bus or the like. However, the PCI family currently does not permit sharing of PCI adapters in topologies where there are multiple hosts with multiple shared PCI buses. As a result, even though such sharing capability could be very valuable when using blade clusters or other clustered servers, adapters for the PCI family and secondary networks (e.g., FC, IB, Enet) are at present generally integrated into individual blades and server systems. Thus, such adapters cannot be shared between clustered blades, or even between multiple roots within a clustered system.
In an environment containing multiple blades or blade clusters, it can be very costly to dedicate a PCI family adapter for use with only a single blade. For example, a 10 Gigabit Ethernet (10 GigE) adapter currently costs on the order of $6,000. The inability to share these expensive adapters between blades has, in fact, contributed to the slow adoption rate of certain new network technologies such as 10 GigE. Moreover, there is a constraint imposed by the limited space available in blades to accommodate PCI family adapters. This problem of limited space could be overcome if a PCI fabric was able to support attachment of multiple hosts to a single PCI family adapter, so that virtual PCI family I/O adapters could be shared between the multiple hosts.
In a distributed computer system comprising a multi-host environment or the like, the configuration of any portion of an I/O fabric that is shared between hosts, or other root nodes, cannot be controlled by multiple hosts. This is because one host might make changes that affect another host. Accordingly, to achieve the above goal of sharing a PCI family adapter amongst different hosts, it is necessary to provide a central management mechanism of some type. This management mechanism is needed to configure the routings used by PCI bridges and PCIe switches of the I/O fabric, as well as by the root complexes, PCI family adapters and other devices interconnected by the PCI bridges and PCIe switches.
It is to be understood that the term “root node” is used herein to generically describe an entity that may comprise a computer host CPU set or the like, and a root complex connected thereto. The host set could have one or multiple discrete CPU's. However, the term “root node” is not necessarily limited to host CPU sets. The term “root complex” is used herein to generically describe structure in a root node for connecting the root node and its host CPU set to the I/O fabric.